Method of manufacture of electron discharge tube grid electrodes



Feb. 14, 1967 w. T. ACKERMANN ETAL.

METHOD OF MANUFACTURE OF ELECTRON DISCHARGE TUBE GRID ELECTRODES FiledMay '7, 1964 "I'll 7 INVENTORJ [V44 75? 74m ie/w/a/f 6%4911-7 l/M[//VOJZ)/ United States Patent Ofiice 33%,859 Patented Feb. 14, 19673,303,859 METHQD (3F MANUFACTURE OF ELECTRQN DISCHARGE GRID ELECTRQDESWalter T. Aclrermann, Millington, and Charles W. Linds= ley, Cresshill,N1, assignors to Radio Corporation of America, a corporation of DelawareFiled May 7, 1964, Ser. No. 365,596 5 Claims. (Cl. 140-715} Thisinvention relates to a method of manufacturing grid electrodes forelectron discharge tubes.

In the manufacture of one type of grid electrode, a plurality of siderods are disposed in cylindrical and parallel array around a mandrel,the mandrel and side rods are axially advanced, and a lateral wire iswound in a helix around the advancing side rods and mandrel. The pitchof the helix is determined by the rate at which the rods are advancedand by the rotational rate at which the lateral wire is wound around theside rods and mandrel. Thereafter, the lateral wire is brazed to theside rods.

In some instance, it is desired that a second or truss winding be woundon top of the lateral wire winding. In the past it has been the practiceto first wind the lateral wire around the side rods, braze the lateralwire to the side rods, and thereafter in a second winding operation,Wind the truss winding over the side rods and lateral wire winding.Then, the truss wire winding is brazed to the lateral wire and side rodsin a second brazing step.

A disadvantage of the prior art method is that it requires two separatewinding operations and two separate brazing operations which add to thecost of the grid.

It is an object of this invention to provide a new and improved methodof fabricating cylindrical electron tube grid electrodes wherein atleast two wire helices are wound simultaneously around the side rods,whereby only a single winding operation and a single brazing operationare required.

It is also sometimes desired that the lateral wire helix be wound with avariable pitch. This is accomplished in the prior art by varying therate at which the side rods and mandrel are advanced. Generally,however, it is desired that the truss winding be wound with a constantpitch. In the prior art, the lateral Wire helix is wound with a variablepitch, the lateral wire is brazed to the side rods, the truss winding isthereafter wound with a constant pitch, and the truss winding is brazedto the lateral wire winding and side rods in a second brazing opreation.

It is a further object of this invention to provide a new and improvedmethod of fabricating cylindrical electron tube grid electrodes whereinat least two wire helices are wound simultaneously around the side rods,and wherein at least one of the helices is wound with a variable pitchwhile at least one other of the helices is wound with a constant pitch.

For achieving the objects of this invention, methods are providedwherein, according to one embodiment of the invention a plurality ofside rods are advanced in circular array past a first and second windinghead, in that order. Each of the winding heads is rotated at a constantrate to wind a Wire around the side rods, the first winding head windinga lateral wire Winding around the side rods, and the second winding headwinding a truss wire winding around the prior wound lateral wire windingand the side rods. No brazing operation is performed between the windingof the lateral wire and the truss wire.

For providing a variable pitch lateral wire winding, incrementalmovements along the direction of advance of the side rods are impartedto the side rods whereby the rate at which the side rods move past thefirst winding head is varied. For providing a constant pitch truss wirewinding, in spite of the variation in the rate of advance of the siderods, the same incremental movements imparted to the side rods areimparted to the second winding head whereby the rate of movement of theside rods relative to the second winding head remains constant.

In the drawings:

FIG, 1 is a side view of a type of electron tube grid which may be madeaccording to this invention;

FIG. 2 is an end View of the grid shown in FIG. 1; and,

FIG. 3 is a side elevational view, partly in section, of apparatus whichmay be used for practicing the methods of this invention.

The cylindrical electron tube grid electrode 10 shown in FIGS. 1 and 2comprises a plurality of side rods 12 arranged in circular cylindricalarray. Surrounding the side rods 12 and brazed thereto is a lateral wirehelix 14. Adjacent each end of the grid 14} the lateral Wire helix 14-is wound with a smaller pitch (as measured by the distance betweenadjacent turns) than along the centrol length of the grid so as toprovide a relatively large number of lateral wire turns adjacent eachend of the grid. The turns of smaller pitch provide greater strength forthe grid electrode. Wound on top of the lateral wire helix 14 is a trusswinding 16 which is brazed to the lateral wire winding and side rods 12.The truss winding 16 is wound with much larger pitch, that is, greateraxial distance between adjacent turns of wire, than the lateral wirewinding and is wound with constant pitch throughout the length of thegrid. The truss winding greatly strengthens the grid structure,

Apparatus for practicing the method of this invention is shown in FIG. 3and comprises a table or base 26 on which a platform 22 is mounted..Platform 22 is supported on a pair of flat rectangular springs 24.Springs 24 permit movement of platform 22 to the right and left, asshown in FIG. 3. The amount of required movement of platform 22 comparedwith the dimensions of platform 22 and springs 24 are such that, for allpractical purposes, the platform 22 moves back and forth along astraight line. For providing the forward and bacl Ward movement ofplatform 22, a cam 26 is provided which engages one end of platform 22.Means for totating the cam is not shown.

Mounted on platform 22 is a mandrel feeding device 28 comprising twopairs 36) and 32 of oppositely disposed rollers. The rollers of eachpair 3t and 32 are spring biased towards one another, and the rollersadvance mandrel sections 36 to the right, as shown in FIG. 3, at aconstant rate. Mandrel feeding devices suitable for feeding mandrels ata constant rate are well known and are not further described.

Also mounted on platform 22, and disposed to the right of mandrelfeeding device 28, is an annular support plate 49 supporting a pluralityof spools 42 (only two of which are shown). Each of the spools 42contains a side rod wire 12 which extends from the spool through acentral hole 44 in plate 40 and towards a mandrel section 36 fed bymandrel feeding device 28 through hole 44 in plate 40.

To the right of plate 4%, but not mounted on platform 22 (being fixedlymounted on table 20 instead and extending over platform 22), is alateral wire win-ding head 43. l/Vinding head 48 comprises a lateralwire supply spool 56 which is supported on an annular rotating disk 52through which the mandrel sections 36 are advanced. To the right ofWinding head 48 is a second or truss wire winding head 56. Winding head56 is similar to winding head 48 except that winding head 56 is mountedon platform 22 for movement therewith. Although only one spool 58 isshown mounted on the annular rotating disc 59 of winding head 56, it issometimes preferable to mount several spools 58 on disc 59. In suchcase, several interspaced truss wire helices are simultaneously wound.

Details of the support plate 40 and winding heads 48 and 56 are notshown since such devices for leading the side rods 12 from spools 42into circular array around the mandrel sections 36, and for winding thelateral wire 14 and truss wire 16 around the side rods 12 and mandrelsections 36 are well known in the art.

A mandrel sections magazine 60 is supported on table 20 to the left ofthe mandrel feeding device 28 and comprises a narrow and elongatedrectangular sleeve 62 for receiving mandrel sections 36. The top andbottom of the magazine sleeve 62 are open. Extending into the openbottom end of sleeve 62 are a pair of rollers 64 which engage thebottom-most mandrel section 36 and advance it through a hole in the wall66 of sleeve 62 and into the mandrel feeding device 28. Magazine rollers64 are operated at a rate tending to feed the mandrel sections 36 at afaster rate than the mandrel sections are fed by the mandrel feedingdevice 28. The rate of advance of the mandrel sections 36 through themandrel feeding device 28, however, is controlled by device 28 becausethe opposing rollers of roller pairs 30 and 32 are spring biased towardsone another while rollers 64 of magazine 60 are frictionally engagedwith the mandrel sections 36.

In the operation of the apparatus described, a string of mandrelsections 36 are first manually fed through mantdrel feeding device 28,hole 44 in support plate 40, and Winding heads 48 and 56. An end of thelateral wire 14 is secured to the mandrel section 36 adjacent windinghead 48 by the use of tape or the like, and an end of the truss wire 16(or wires, if several are used) is likewise secured to the mandrelsection 36 adjacent winding head 53. The apparatus is then energized.Rollers 64 of magazine 69 and roller pairs 30 and 32 of the mandrelfeeding device 28 are rotated whereby the mandrel sections 36 are drivenpast the winding heads 48 and 56. The mandrel sections 36 passingthrough the winding heads 48 and 56 are pushed along by the followingmandrel sections. Also, the spools containing the lateral wire 14 andthe truss wire 16 are caused to rotate around the mandrel sections at aconstant rate.

Ignoring, for the moment, the movement of platform 22, the side rods 12are unspooled from spools 42 and advance through and past winding heads48 and 56. Rotation of the lateral wire 14 around the advancing siderods 12 and mandrel sections 36 winds the lateral wire helix around theside rods 12. Likewise, rotation of the truss wire 16 around the mandrelsections 36 causes the truss wire to be wound in .a helix on top of thelateral wire helix already wound. In the absence of movement of platform22, both the lateral wire 14 and the truss wire 16 are wound withconstant pitch.

For providing a variable lateral wire winding pitch, platform 22 ismoved by cam 26. Since the lateral wire winding head 48 is stationary,movement of platform 22 to the right, as shown in FIG. 3, causes anincrease in the rate of advance of mandrel sections 36 and side rods 12past winding head 48. The increased rate of advance of mandrel sections36 and side rods 12 causes the lateral wire 14 to be wound withincrease-d pitch. Conversely, while platform 22 moves to the left, asshown in dashed lines in FIG. 3, the pitch of the lateral wire windingis decreased.

Since winding head 56 and mandrel feeding device 28 are both mounted onplatform 22, movement of platform 22 in either direction has no affectupon the rate of advance of the mandrel sections 36 and the side rods 12past winding head 56. Thus, regardless of the changes in the rate ofadvance of mandrel sections 36 and side rods 12 with respect to thelateral wire winding head 48, the

truss wire winding head 56 winds the truss wire 16 with a constantpitch.

As shown, magazine 60 is mounted on table 20 and does not move withplatform 22. Upon movement of platform 22 to the right, as shown in FIG.3, the mandrel section 36 still engaged with the magazine rollers 64 isadvanced at a sufficiently fast rate by rollers 64 to maintain the endof this mandrel section 36 in contact with the end of the mandrelsection engaged with and being fed by the mandrel feeding device 28.Upon movement of platform 22 to the left, rollers 64 of magazine 60 slipagainst the mandrel section being \fed by these rollers while stillmaintaining a sufficient rate of advance of the mandrel section tomaintain it in engagement with the mandrel section being fed by rollerpairs 30 and 32 of device 23.

For winding the lateral wire helix 14 with two constant pitches, asshown in FIG. 1, cam 26 has a development suitable to cause platform 22to advance and return at constant speeds. Suitable variations forwinding the lateral wire helix 14 with different pitches will beapparent to persons skilled in the art.

After the winding operations, the lateral and truss windings are brazedto the side rods and one another in a single brazing operation; the siderods, lateral wire, and truss wire are cut through at the ends of themandrel sections 36; and the cylindrical grids 10 are slid off themandrel sections 36. Preferably, the side rods 12, lateral wire 14, andtruss wire 16 are copper plated. Upon heating, the copper melts toprovide the brazed joints. The mandrels are made of a materialnon-wettable by copper, such as a nickel-chrome alloy commercially knownas Nichrome.

What is claimed is:

1. A method of fabricating a cylindrical grid having a lateral wirewound around a plurality of side rods and a truss wire wound over saidlateral wire, said method comprising advancing said side rods incylindrical array past a pair of winding heads, rotating said windingheads around said side rods at a constant rotational rate for winding apair of helices around said side rods, and incrementally moving saidside rods and one only of said winding heads relative to one anotheralong the axis of advance of said side rods for changing the rate ofadvance of said side rods and said one winding head relative to oneanother while not changing the rate of advance of said side rodsrelative to said other winding head.

2. A method of fabricating a cylindrical grid having a lateral wirewound around a plurality of side rods and a truss wire wound over saidlateral wire, said method comprising advancing said side rodsincylindrical array past a pair of winding heads, rotating said windingheads around said side rods at a constant rotational rate for winding apair of helices around said side rods, and incrementally moving saidside rods and one only of said winding heads along the axis of advanceof said side rods for changing the rate of advance of said side rodspast the other of said winding heads while not changing the rate ofadvance of said side rods past said one winding head.

3. A method of fabricating a cylindrical grid having a lateral wirewinding around a plurality of side rods and a truss wire winding woundover said lateral wire Winding, said method comprising advancing saidside rods in cylindrical array successively past first and secondwinding heads, rotating said winding heads around said side rods at aconstant rotational rate for causing said one winding head to wind alateral wire helix around said side rods and for causing said secondwinding head to wind a truss Wire around said lateral wire winding andsaid side rods, and incrementally moving said side rods and said secondwinding head only along the axis of advance of said side rods forchanging the rate of advance of said side rods past said first windinghead while not changing the rate of advance of said side rods past saidsecond winding head.

4. A method of fabricating a cylindrical grid having a lateral wirewinding around a plurality of side rods and a truss wire winding woundover said lateral wire Winding, said method comprising advancing saidside rods in cylindrical array successively past first and secondwinding heads, rotating said winding heads around said side rods at aconstant rotational rate for causing said one winding head to Wind alateral wire helix around said side rods and for causing said secondwinding head to wind a truss wire around said lateral wire winding andsaid side rods, incrementally moving said side rods and said secondwinding head only along the axis of advance of said side rods forchanging the rate of advance of said side rods past said first windinghead while not changing the rate of advance of said side rods past saidsecond winding head, thereafter brazing said side rods, lateral wire,and truss wire to one another, and cutting through said side rods,lateral wire and truss wire at spaced intervals to provide individualgrids.

5. A method of fabricating a cylindrical grid having a lateral wirewinding around a plurality of side rods and a plurality of interspacedtruss wire windings wound over said lateral Wire winding, said methodcomprising advancing said side rods in cylindrical array successivelypast first and second winding heads, rotating said winding heads aroundsaid side rods at a constant rotational rate for causing said onewinding head to Wind a lateral wire helix around said side rods and forcausing said second winding head to wind a plurality of interspacedtruss wires around said lateral wire winding and said side rods,providing said side rods and said second winding head only withincremental movements along the axis of advance of said side rods forchanging the rate of advance of said side rods past said first windinghead While not changing the rate of advance of said side rods past saidsecond Winding head, thereafter brazing said side rods, lateral wire,and truss wires to one another, and cutting through said side rods,lateral wire and truss wires at spaced intervals to provide individualgrids.

References Cited by the Examiner UNITED STATES PATENTS 1,999,654 4/1935Cobb 71.5 2,422,827 6/1947 Drieschman et al. 14071.5 2,441,228 5/1948Schneider et al. 140-71.5 3,124,169 3/1964 Schade 140--71.5 3,139,1206/1964 Beezer et al 14071.5

WILLIAM J. STEPHENSON, Primary Examiner.

1. A METHOD OF FABRICATING A CYLINDRICAL GRID HAVING A LATERAL WIREWOUND AROUND A PLURALITY OF SIDE RODS AND A TRUSS WIRE WOUND OVER SAIDLATERAL WIRE, SAID METHOD COMPRISING ADVANCING SAID SIDE RODS INCYLINDRICAL ARRAY PAST A PAIR OF WINDING HEADS, ROTATING SAID WINDINGHEADS AROUND SAID SIDE RODS AT A CONSTANT ROTATIONAL RATE FOR WINDING APAIR OF HELICES AROUND SAID SIDE RODS, AND INCREMENTALLY MOVING SAIDSIDE RODS AND ONE ONLY OF SAID WINDING HEADS RELATIVE TO ONE ANOTHERALONG THE AXIS OF ADVANCE OF SAID SIDE RODS FOR CHANGING THE RATE OFADVANCE OF SAID SIDE RODS AND SAID ONE WINDING HEAD RELATIVE TO ONEANOTHER WHILE NOT CHANGING THE RATE OF ADVANCE OF SAID SIDE RODSRELATIVE TO SAID OTHER WINDING HEAD.